The entertainment industry requires that lights and light modifying elements such as color changers be moved. Motors and other moving elements, however, are inherent sources of noise. The inventors of the present invention realized that silent operation is highly desirable so that an audience watching a theater production will not be disturbed.
However, there is a trade-off between the speed of movement of various elements and the amount of noise that they produce. Belts and pulleys can be just as noisy as gears, depending on the speed and quality. Belts and pulleys are very noisy when running fast. The first stage of a reduction train runs at speeds which are typically above 1500 rpm. This high speed operation invariably produces noise. At speeds below 1500 rpm, belt and pulley systems become much quieter. This is especially true when noise-reducing mechanisms, such as special tooth-cutting methods, are used. The belt and pulley uses a rubber belt to transmit the force from the driving pulley to the driven pulley. The belt and pulley inherently has low noise transmission and noise vibration. The damping effect of the belt in essence minimizes the transmission of noise and vibration.
Gears, on the other hand, transmit noise directly from the driving gear to the driven gear due to direct contact between the teeth.
The inventors recognized that belts do a very good job of preventing noise transmission so long as they are going slow. The inventors realized, therefore, that a belt in the final stage of the reduction train would help quiet the system. The high speed portion will inherently have noise therein. Since both gears and pulleys will cause noise, the inventors recognized that the quietest solution for the high speed portion is to use small plastic gears with small teeth. This portion will inherently have noise therein.
It is an object of the present invention to isolate this noise and prevent it from traveling through the rest of the system.
The inventors of the present invention noticed that such noise, although often masked by the sounds of the theater production, can prove very bothersome to the user. In order to obviate this problem, the inventors determined that a certain combination of elements minimizes the noise from such systems.
A preferred embodiment uses a connection between an output shaft of a motor and a pulley which is formed using an anti-noise element combination. The pulley is then connected via a belt to a driven shaft. One element of the anti-noise element combination includes a flexible coupling system which has inner surfaces which are substantially the same shape as the outer surface of the driving shafts. Typically these driving shafts are cylindrical. The flexible coupling has elements allowing tightening of these surfaces around the driving shaft. When a specific end of the coupling is tightened, it contracts in size around the shaft, thus tightly gripping the shaft.
Many different kinds of couplings are used. The most preferably used one includes a plurality of circumferential cuts through the middle portion. These cuts, and the material of the coupling, contribute to the ability of the flex coupling to flex in directions which are perpendicular to the axial direction. This has the advantage of minimizing the amount of direct physical noise across the coupling. Rubber grommets are preferably used to minimize driving motor and the plates supporting the pulley system.
The inventors also recognized that misalignment of shafts tends to cause even more noise, e.g. "creaks" and "groans". Another aspect addresses these problems adaptively adjusting a position of the output axis in a way that minimizes these problems.
Another aspect of the invention relates to tensioning an endless loop element which drives a light modifying element of a stage lighting device. The device has a light source for emitting light and a light modifying element for modifying such light. The light modifying element is coupled to a driven element which is rotationally coupled to a structural member so as to be rotatable about a first axis. The device has a noise-producing motor assembly with an output shaft. A driving element is coupled to the output shaft to be rotationally driven by the output shaft about a second axis. The driving element is coupled to the driven element by an endless loop element so as to rotationally drive the driven element about the first axis.
A vibration-isolating mounting structure couples a motor assembly to the structural member and includes surfaces which vibrationally isolate the motor assembly from the structural member to attenuate vibration transferred from the motor assembly to the structural member. The mounting structure is pivotally coupled to the structural member with a pivotal range of motion about a pivot axis which is substantially parallel to the first axis. A tensioner couples the structural member to the mounting structure to bias the mounting structure in a first direction about the pivot axis so as to maintain a tension in the endless loop element.